Subj : Re: Assigning an l-value expression programmatically
To   : netscape.public.mozilla.jseng
From : Brendan Eich <brendan@meer.net>
Date : Tue Oct 21 2003 01:42 pm

Harizakis Costas wrote:

>  Hi,
>
>  I would like to ask if there is a way to perform programmatically the
>following ...
>
>foo.bar.i = "value";
>
>  ... given that I have access to the left and right parts of the
>assignment - say the strings "foo.bar.i" and "value".
>
>  Let me re-phrase my question in a more general form: Suppose that I have 2
>JavaScript expressions. The 1st holds the left part of the assignment
>(l-value expression) and the 2nd holds the right part of the assignment
>(r-value). Using the JS_ExecuteScript(...) I can evaluate a jsval for the
>r-value. How can I gain access to the object/property pair (l-value) which
>is the receiver of the evaluated r-value?
>
>  My actual problem arises when I have the l-value in a string form, the
>r-value already evaluated (as a jsval) and I want to assign the latter on
>the former.
>  
>

I'm curious why you have the left-hand side in a string -- is that 
something a user types in?  Do you have to check that it's well-formed?  
Could it be arbitrariliy complex (a[i+4][j/2].b.c[k*3].d, e.g.)?

If you have the right-hand side as a string, the easiest course, which 
wins also if you need syntax checking, is to concatenate the LHS, " = 
(", the RHS, and ")" and then JS_EvaluateString.

There is no API to evaluate an lvalue.  It seems better to understand 
the problem you're solving before saying more.

/be

.